This authoritative collection brings together a careful selection of previously published articles that use economics to analyze the interaction of law, on the one hand, and social norms and nonlegal sanctions on the other. The articles cover a range of foundational questions. What are social norms and nonlegal sanctions? Do strong laws undermine social norms, thus weakening other valuable forms of social cooperation? Can laws be used to exploit existing social norms, so that the laws are more effective than they would be otherwise? The contributing authors use a variety of economic models and concepts to address these questions.